Method for RF card detection in a contactless system

Abstract

A method and processor-readable storage medium for performing the method of identifying RF cards in a card reader's field. Polling requests are sent to cards in a card reader's field. Where a clear response from the sent command is received from a responding card, the response is saved, the responding card moved to an Active state, and the timeslot number incremented if possible and the above steps repeated until no clear response is received. Where no clear response is received, a determination of whether a collision has occurred is made. If no collision occurred, the timeslot number is incremented; if a collision did occur, another polling request is sent. Discovered cards are returned when no cards or collisions are detected after every timeslot is polled.

Description

FIELD OF THE INVENTION [0001] This invention relates to detecting RF cards within an RF card reader's field. BACKGROUND ART [0002] Radio frequency identification (“RFID”) is becoming increasingly common. RFID uses wireless radio communications to identify and collect information about objects. Information about an object may be created or updated “on the fly” after the object is identified. RFID may be used in a wide range of applications including identity cards. [0003] RFID systems consist of one or more readers and transponders, contactless memory tags that communicate with the reader. Transponders may be carried on identity cards. The transponders contain data allowing the card to be identified and are made of a memory associated with a radio frequency communication block. The reader is connected to an antenna which transmits and receives the radio frequency signal to and from the transponders. In FIG. 1, a reader 68 of the prior art may communicate with all the cards 70, 72, 74...

AI Technical Summary

Benefits of technology

The patent describes a method for identifying RF cards in an RF card reader. The method involves sending a series of commands to the cards in the field, and then checking for a clear response from each card. If there are no collisions (when multiple cards respond to the same command), the method continues until all cards have been identified. The technical effect of this method is to improve the speed and accuracy of identifying RF cards in an RF card reader.

Problems solved by technology

When a reader communicates with the transponders or cards within its fields, collisions occasionally occur if more than one transponder or card tries to reply to the reader at the same time.

However, using this approach, the presence of multiple cards may not be detected until the responding card is removed from the field or the state where it can respond to requests from the reader.

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